Concrete mixer with tub lift



5, 1964 P. AUGUST ETAL 3,145,976

CONCRETE MIXER WITH TUB LIFT Filed May 24, 1961 2 4 Sheets-Sheet l 3 u INVENTORS J MM M M 49 /8 BY 2: /;Z7 f? Aug. 25, 1964 Filed May 24, 1961 P. AUGUST ETAL CONCRETE MIXER WITH TUB LIFT 4 Sheets-Sheet 2 IN V EN TOR5 M w/wig! W7 ill 25, 1964 P. AUGUST ETAL CONCRETE MIXER WITH TUB LIFT 4 Sheets-Sheet 3 Filed May 24, 1961 4 Sheets-Sheet 4 P. AUGUST ETAL CONCRETE MIXER WITH TUB LIFT Aug. 25, 1964 Filed May 24, 1961 United States Patent 3,145,976 CONCRETE MIXER WITH TUB LIFT Pablo August and Ingeborg Wolfes dc August, both of Directorio 130, Bernal, Bueuos Aires, Argentina Filed May 24, 1961, Ser. No. 112,456 14 Claims, (Cl. 259-160) The present invention relates to certain new and useful improvements in concrete mixers of the type comprising a tub lift with a rotary mixing device arranged in the tub of the lift as disclosed in our co-pending application Serial No. 73,849, and more particularly refers to an improved winch mechanism for operating both the mixing device and the tub lift.

As clearly set forth in our said prior specification, for producing good mixtures and for increasing the output of the mixer, the operation of the mixing device has to continue while the mixing tub of the lift is moved from its lower charging position to its upper discharging position. Therefore, the winch mechanism has to impart rotation to the mixing device not only during the time of charging the tub in its lower charging position, but also during the time of hoisting the tub to its upper discharging position. In connection herewith it will be appreciated that for mechanical reasons the speed of the mixing device and the hoisting speed of the tub lift can not be arbitrarily increased, but that mixture quality and mixer output depend upon the continuation of the mixing operation during the upward movement of the mixing tub. The winch mechanismin accordance with our basic invention has been so designed as to comply with the requirements in as far as mixing time and the mixing and hoisting speeds are concerned. Practice, however has taught that the same tends to hoist the mixing tub without simultaneously rotating the mixing device in said tub. Further, during operation of the mixer, particularly during the operations of lifting and lowering the mixing tub, the two ropes of the winch mechanism are not maintained under equal constant tension and one or the other of said ropes is liable to lose contact With the helical guide grooves of the pulley of the mixing device in said mixing tub jumping from one volution to the second or third next volution of said helical grooves and thus affecting the correct operation of the mixer. Finally, due to the specific operation of said winch mechanism the ropes and the tub of the lift are subject to jerks liable to increase tear and wear and of correspondingly shortening the lifetime of the machine.

The main object of our present invention is to provide an improved winch mechanism for operating both the mixing device and the tub lift of a concrete mixer having a tub lift with a rotary mixing device arranged in the tub of said lift, said winch mechanism comprising a pair of rope pulleys of large diameter on the ends of the shaft of the said mixing device, a pair of ropes passing in several turns around said pulleys, a ropeguiding device provided on each of these pulleys, a pair of composite rope drums fixedly mounted on a common driving shaft for the operation of said ropes, each composite rope drum comprising two drum portions for fastening on .each of these drum portions one of the two free ends of the respective rope, and at least one of said drum portions being constructed as a twostep drum portion, the two steps of which are of different diameter.

. Another object of the invention is to provide an improved winch mechanism as above set forth, wherein each of the said composite rope drums includes a normal cylindrical drum portion and a two-step drum portion, the two steps of the latter being of different diameter and interconnected by a conical transition portion and 3,145,976 Patented Aug. 25,1964

the diameter of the smaller drum step being substantially equal the diameter of said cylindrical drum portion.

A further object of the invention is to provide an improved winch mechanism as above set forth, wherein each of the said composite rope drums includes a conical drum portion and a two-step drum portion, this two-step drum portion having one step formed by a cylindrical body and the second step by a deep annular groove provided at one end of said cylindrical body, the width of said groove being equal the thickness of the ropes of the winch and the diameter of said groove on its bottom being substantially smaller than that of the smaller end of said conical drum portion.

Still another object of the invention is to provide an improved winch mechanism as above set forth, wherein each of the said composite rope drums includes a first drum portion constituted by a grooved rope pulley, the circumferential groove of which is relatively deep and has a width equal the thickness" of the ropes of the winch, and a second drum portion constituted by a two-step drum portion having one step formed by a cylindrical body and the second step by a deep annular groove provided at one end of said cylindrical body, the width of said groove being equal the thickness of the ropes of the winch and the diameter of said groove at its bottom being substantially smaller than that of the groove bottom of the pulley of said first drum portion.

The two composite rope drums fixedly mounted on a common driving shaft not only simplify the construction of the machine, but also allow for the provision of an increased diameter of the rope pulleys on the shaft of the mixing device with the result that rotation of the latter during the hoisting operation of the tub lift is ensured.

An additional object of the invention is to provide an improved winch mechanism as above set forth, wherein one of the said two composite rope drums has a normal cylindrical drum portion and a two-step drum portion is associated with a similar composite rope drum fixedly mounted on the driving shaft of said two composite rope drums, for operating a rope and tackle control device capable of absolutely preventing the said mixing tub from being lifted without its mixing device being simultaneously operated by the pair of ropes connected to and operated by said two composite rope drums.

' A rather important advantage secured by the improved winch mechanism as hereinbefore set forth consists in that the mixing tub, not only during lifting and lowering but also in its lower charging position remains practically elastically suspended by the ropes of the Winch mechanism, whereby the prejudicial jerks are substantially avoided. These jerks are absolutely avoided by the provision of a drum portion of the said composite rope drums capable of winding up the rope with increasing diameter, with the advantageous result that hoisting of the mixing tub is effected with gradually increasing speed, while lowering of the mixing tub proceeds with gradually decreasing speed and that braking means may be dispensed with.

Still another object of the invention is to provide an improved winch mechanism as above set forth, wherein the pulleys of the mixing device in, the said mixing tub are provided with rope-guiding means in form of a cylindrical casing movably arranged around each of said pulleys and provided with openings for the entrance and exit of said rope and with guide means capable of causing said casing to follow the movements of said rope on said pulley.

With these objects and advantageous features in view, the present invention will now be fully described with reference to the accompanying drawings which schematically illustrate by Way of example several embodiments of the invention.

FIGURES 1 and 2 show in a front view and in side view, respectively, a concrete mixer incorporating the improved winch mechanism according to the invention in a first embodiment thereof;

FIGURE 3 is an enlarged detail view showing one of the composite rope drums according to FIG. 1, which is associated with a similar composite rope drum forming part of a rope and tackle control device;

FIGURES 4 and 5 are enlarged detail views similar to FIG. 3, showing two further embodiments of composite rope drums, however, without the said additional composite rope drum, and

FIGURE 6 is a schematic view showing a further embodiment of rope drum operatively connected with a rope pulley of the mixing device;

FIGURES 7 and 8 show one of the pulleys of the mixing device provided with a rope-guiding device in side view and front view, respectively.

In the concrete mixer as illustrated by the accompanying drawings, the machine frame A, the mixing trough B formed by the transport tub of a tub lift and the guide rails C of the tub lift are of identical constructions as described and shown in our prior specification above referred to.

At the top of the frame A only one driving shaft 1 is rotatively mounted and operatively connected with a driving engine (not shown), for which purpose a sprocket wheel 11 or pulley may be provided on said shaft.

The driving shaft 1 carries at each end a composite rope drum 2 comprising a first normal cylindrical drum portion 4 provided with suitable flange disks 5, and a two-step drum portion composed of a smaller drum step 3 and a larger drum step 3b and an intermediate conical transition portion 3a, the smaller drum step 3 having a diameter substantially equal the diameter of the cylindrical drum portion 4 and said smaller drum step 3 together with said conical transition portion 3a being provided with a helical rope-guiding groove which, if desired, may continue on the larger drum step 3b.

The mixing trough B is provided with two rope pulleys 7 fixedly mounted on the shaft 6 of the mixing device M in said trough. These pulleys 7 are also provided with helical rope-guiding grooves as indicated at 8 for the ropes 9.

By virtue of the larger drum steps 3a of the composite rope drums 2, the diameter of the rope pulley 7 may be practically doubled as compared with the diameter of the pulleys according to the basic invention and the lever arm acting on the mixing device thus is advantageously increased.

With the mixing trough B in its lower position, one end of each rope 9 is fastened at 9a (FIG. 2) on the helically grooved drum step 3 and laid in several turns around the grooved rope pulley 7, whereafter the rope is returned to the composite rope drum 2 where it is wound up on the cylindrical drum portion 4 in so many or more turns as revolutions are to be made by the pulley 7 for lifting the mixing tub B to its upper discharging position and where its free end is fixed on said drum portion 4. The arrangement of the rope 9 with regard to the composite rope drum 2 is such that, for instance, while the rope is uncoiled from the drum portion 4 it is wound up on the two-step drum portion 3-3b and vice-versa.

When the mixing trough B is in its lower charging position and the rope 9 is arranged as above described, during operation of the driving shaft 1 in the direction indicated by the arrow, the rope 9 is uncoiled from the drum portion 4 and wound up on the drum portion 3-311. By virtue of cylindrical drum portion 4, the rope length uncoiled from this drum portion 4, equals that wound up on the drum step 3, so that the shaft 6 of the mixing device M is caused to rotate, but the mixing trough or tub B is not lifted. However, as the shaft 1 continues rotating in the same direction and the rope 9 on the drum step 3 is caused to follow the helical guide groove on the conical transition portion 3a and is wound up on the larger dum step 3b, then more rope is wound up on this larger drum step than is uncoiled from the drum portion 4, with the result that now the mixing tub B is lifted and simultaneously the shaft 6 of the mixing device M is caused to continue rotating.

The difference between the diameters of the larger drum step 3b and of the normal cylindrical drum portion 4 is so selected that again the desired lifting speed as set forth in the specification of the prior invention is attained. By virtue of the fact that now the diameter of the drum step 3b is approximately twice the diameter of the drum step 3, the rope is wound up thereon with a correspondingly increased speed and consequently passes around the pulley 7 with the like increased speed. It is for this reason that according to the invention the diameter of this pulley 7 may be approximately doubled, thereby maintaining the speed of the mixing device and reducing to about one half the traction force required for the operation of the mixing device. Consequently the danger of the mixing device becoming inoperative while the mixing tub is being lifted, is minimized.

In order to entirely abolish this danger, the present invention includes a rope and tackle control device. This device comprises a composite rope drum 13, 14 similar to the composite rope drums 2 which is fixedly mounted on a corresponding extension of one end of the driving shaft 1, a rope 23 adapted to be wound up on one drum portion and simultaneously uncoiled from the other drum portion of said composite rope drum, a tackle pulley engaged by said rope 23, a link member 16 carried by said pulley and a connecting rope 17, which guided by suitably arranged loose guide pulleys 18, is connected at 19 with the mixing trough or tub B.

In the lower position of the tub B the rope 23, having its ends respectively fastened on the two-step drum portion 13-13b and on the cylindrical drum portion 14, is wound up on said two-step drum portion 13, whereas the drum portion 14 is empty or almost empty. When the shaft 1 rotates, the rope 23 is uncoiled from the drum portion 13-13b and wound up on the drum portion 14. In view of the fact that the rope 23 is first uncoiled from the smaller drum step 13, the uncoiled rope length is simultaneously wound up on the drum portion 14. When thereafter the rope is uncoiled from the larger drum step 13b, a certain rope length is set free corresponding to the lifting height of the mixing tub B, so that during this partial uncoiling from the drum step 13b the mixing tub may be lifted by the rope 9 with control effect exerted by the device 13-18, whereas during the uncoiling from the drum step 13 the tub B is retained in its lower position. In other words, lifting of the mixing tub B without the operation of the mixing device is rendered impossible. If the rope tends to lift the mixing tub, without rotating the mixing device, in the absence of the tackle effect the tub would be lifted with the double speed. This is now rendered impossible, because by the rope 17 the tub is prevented from moving upwards with a greater speed than that desired and admitted by the tackle effect. In this case the device 13-18 assures that the force for lifting the tub becomes greater than that for rotating the mixing device. As already stated, at first in the lower position of the mixing tub, equal length of the rope 23 is uncoiled from the drum portion 13 and wound up on the drum portion 14, the position of the loose pulley 15 remains unaltered and the mixing tub B is retained in its lower position, the mixing device being operated without the mixing tub being lifted.

On the other hand, as soon as the rope 9 is wound up over the conical transition portion 3a on the larger drum step 311 of the composite rope drum 2, the rope 23 is uncoiled from the larger drum step 13b of the composite rope drum 13, 14. Therefore, only in dependence of this uncoiling of the rope 23 and of the corresponding downward movement of the loose pulley 15, the rope 9 is allowed to lift the mixing tub. It will be appreciated that thus the mixing trough or tub B in all its positions i.e. in its lower position as well as during lifting and lowering, remains practically suspended by the ropes 9 and 17 and is unable to increase its lifting speed by causing the ropes 9 to slide on the rope pulleys 7.

It will further be appreciated that the construction of the mixer is simplified insofar as but one driving shaft 1, instead of two, is required, although the mixing trough is operated by a pair of ropes 9 and controlled by a rope and tackle device 13-18.

In FIGURE 2, the reference numeral 20 indicates the rope 9 'to be wound up on the smaller drum step 3 at the beginning of the mixing operation without the tub B being lifted, 21 indicates the rope 9 at the beginning of the tub-lifting operation i.e. when the rope is wound up on the larger drum step 3b, and 22 indicates the rope 9 being uncoiled from the drum portion 4. These positions correspond to the start of the lifting operation. When the tub B starts its downward movement, the reference numerals 20 and 21 are to be changed to 21 and 20, respectively.

The embodiments of the composite rope drums as shown in FIGURES 4 and 5 incorporate the characteristic feature of gradually varying the hoisting and lowering speed of the mixing tub by changing the diameter of uncoiling and winding up the ropes of the winch mechanism.

With reference to FIGURE 4, the composite rope drum comprises a first drum portion 44 provided with suitable flange disks 45 and a second two-step drum portion 43. The first drum portion 44 in this case is coneshaped and conveniently provided with a helical ropeguiding groove 46, whereas the second drum portion 43 is formed by a cylindrical body which at one end is provided with a deep annular groove 43a. This groove has a width equal the thickness of the rope 60 (FIG. 6), so that it only can receive the rope in superposed windings. The cylindrical body 43 constitutes one drum step and the groove 43a constitutes the second drum step of the two-step drum portion, whereon one end of the rope 49 is fastened on the bottom of said groove. The bottom of this annular groove has a diameter substantially smaller than that of the cone-shaped drum portion at its smaller end. The two-step drum portion is conveniently formed with flanges 47.

In the embodiment according to FIGURE 5, the first drum portion 54 is constituted by a grooved rope pulley, the distance between the flange disks 55 being equal the thickness of the rope 60 (FIG. 6) and annular groove 56 formed thereby being of substantial depth. The diameter of the bottom of this annular groove is the same as that of the smaller end of the cone-shaped drum portion 44 (FIG. 4). The second drum portion 53 is again a twostep drum portion, its parts 53 and 53a being of identical construction of the two-step drum portion 43, 43a (FIG. 4).

FIGURE 6 shows a composite rope drum the two portions of which are two-step portions like that 53, 53a of FIGURE 5, and its operative connection with a pulley of the mixing device. In this embodiment the two drum steps are formed each by a cylindrical body 57, 58 and by an annular groove 57a, 58a, said two cylindrical bodies and these two grooves being of diiferent diameters and the width of the grooves being equal the diameter of the rope 60 which connects the rope drum with a pulley 61 of the mixing device, said pulley having a circumferential groove of a width capable of receiving a determined number of rope windings. If the rope has a diameter of e.g. 8 mm. and the pulley has to receive four adjacent rope windings, the width of the groove 62 of the pulley has to be 32 mm., the groove being laterally defined by tapered flanges 63. As clearly shown in FIG. 6, the distance between the component portions of the composite drums is larger than the width of the pulley groove 62. Consequently the rope 60 is conducted to the pulley 61 under certain angle substantially corresponding to that of the tapered flanges 63, whereby the rope 60 is caused to form adjacent and not superposed windings on the pulley.

The operation of the winch mechanism and of the mixer provided therewith as shown in FIGURE 6 is as follows: The mixing tub B is disposed at the level suitable and desired for the tub-charging operation. In this position of the tub B, one end of the ropes 60 is fixed on the bottom of the groove 57a of the composite rope drums. The ropes are then wound up in superposed windings in said grooves until completely filling the same and thereafter are additionally wound up in several adjacent windings on the cylindrical bodies 57. Now the ropes are led downwards to the pulleys 61 and, after filling the grooved bottom of each pulley with adjacent rope windings, they are again led upwards and their free ends are secured on the bottom of the groove 58a. Thus the mixer is in condition ready for operation.

During the tub-charging operation, the engine (not shown) operatively connected with thecommon driving shaft of the composite rope drums is started. The rotation of these drums causes each rope 60 to be uncoiled from the drum portion 57 and to be wound up on the drum portion 58. During the uncoiling of the rope 60 from the cylindrical body 57, the diameter of which is somewhat larger than the first rope winding in the groove 58a the rope pulleys 61 and therewith the mixing device are caused to rotate, but the mixing tub B is not lifted. On the contrary, during this initial mixing operation, the tub may be slightly lowered to yieldingly absorb the impact stresses of the tub-charging operation, if the diameters of the rope drum portions 57, 57a; 58, 58a are correspondingly selected.

If the diameter of the semi-circle of the rope 60 on the cylindrical body 57 is 300 mm. and that of the rope on the bottom of the groove is 272 mm. and the rope has a diameter of 7 mm. the rope being uncoiled from said body 57 and Wound up in said groove 58a the displacement of the mixing tub is as clearly set forth in the following table:

Diameters of the Tub rope windings nntravel per Total coiled from or revolutub Revolution of the wound up on drum tion, travel, composite drums portions, mm. cm. cm.

Downwards 53a, 58 Upwards As will be clearly understood from the preceding table, when starting the operation of the mixer, there is at first a slight downward movement of the mixing tub due to that at first the cylindrical body 57 uncoils a larger rope length than that wound up in the groove 58a. After two revolutions of the composite rope drums the upper winding in the groove 58a has already a diameter of 300 mm. so that during the third revolution the tub is not moved at all. Until the fifth or sixth revolution the upward movement of the mixing tub is small, because the diameter of the rope windings on the composite drums only changes in the groove 58a whereas their diameter on the cylindrical body 57 remains constant. From the seventh revolution of the composite rope drums the situation changes, the difference between the diameter of each rope winding uncoiled from the groove 57a and that wound up in the groove 58a gradually increases from one revolution to the next one. Consequently the tub travel as well as the hoisting speed also increase. From the eleventh revolution the rope 69 is wound up on the cylindrical body 58 and the difference between the diameter of the rope windings is reduced by virtue of that the diameter of the Windings on said cylindrical body is now constant.

According to the diameter of the rope 60, to the length of the cylindrical body 57, 58 and to the depth of the grooves 57a, 581) the times during which the tub lift B remains at its lower charging position and within which the same is lifted and lowered may be predetermined and thereby the time available for mixing may be changed and adjusted.

On the other hand, it will also be appreciated that in accordance with the example as above described at the fourteenth revolution the tub reaches a height of 195.8 em, but after the sixteenth revolution the height of the tub already amounts to 268.4 cm., with the advantageous result that if a greater lifting height is required, the time of operation of the mixer per batch is not proportionally increased.

According to the characteristics of the building ground, the charging position of the tub lift may be higher or lower and sometimes it will be convenient to make an excavation in the earth in order to lower the charging position of the tub; in this way the lifting height may be doubled. The mixer provided with the improved winch mechanism is so designed that for the practically smallest lifting height 14 revolutions are required for reaching this height and proved to be sufficient for obtaining a good concrete. If the lifting height reaches a maximum of about 3 m., the hoisting time will be increased for about 2 to 3 seconds only, so that a batch may be thoroughly mixed within practically the same period of time, particularly if as aforesaid the number of rope windings on the cylindrical bodies 57 is changed correspondingly.

When the mixing tub B moves downwards, its displacement proceeds in the inverse manner i.e. with a gradually decreasing speed, which means that the tub will move downward at first with relatively high speed and this speed will decrease as the tub approaches its lower position. By virtue of that during the last revolutions of the composite drums the tub moves a little upwards, thereafter, it automatically comes to a standstill without being stopped by the motor or braked by a special brake means. This is advantageous insofar as in a completely automatic operation of the mixer the downward movement of the tub may be effected without connecting the motor and thus two additional switches, contactors or electric control elements for the reverse motion of the motor or downward movement of the tub may be dispensed with.

Referring to FIGURES 7 and 8, the rope-guiding device provided according to the invention on each of the pulleys 7 of the mixing device in the mixing tub B, comprises a cylindrical casing 71 which conveniently consists of two semi-cylindrical halves provided with suitable known clamp means or the like for their removal interconnection and the movable arrangement around the pulley 7. The casing 71 is provided with a small opening 72 and with a larger opening 73, constituting the entrance and exit openings for the rope 9.

If the pulley 7 is provided with a helical guide groove 8, the casing 71 comprises inwardly projecting guide pins indicated at 74 which engage said guide groove 8. If the pulley 7 has a plain circumference, said pins are conveniently replaced by small rollers or preferably by loosely mounted balls in contact with the circumference of the pulley.

In the zone of the opening 72 the casing 71 is provided with a guide arm 75 which in a downwardly projecting edge portion 76 forms a guide loop 77 for the rope 9.

While the rope 9 passes around the pulley 7 along its guide groove 8 or on the plain circumference of the same, the same is displaced laterally with regard to FIG. 7 and while the mixing tub B is lifted and lowered, the angle formed between the rope 9 and the horizontal will slightly vary and the rope is also displaced in this direction. The casing 71 has to follow these displacements of the rope 9 and for this purpose the guide arm 75 is provided. This guide arm 75 not only imparts the casing slight rotary motions, but also causes the same to move to and fro in axial direction, wherein the casing 71 is simultaneously guided by the pins 74.

In view of the fact that the casing 71 is arranged in close proximity with the circumference of the pulley 7, the same effectively prevents the rope 9 from losing its contact with the pulley and from jumping from one volution to the second or third next volution of the helical guide groove 8.

In the case of a plain circumference of the pulley, a helical guide groove for the rope may be provided on the inner wall of the casing 71.

What we claim is:

1. A concrete mixing and lifting apparatus comprising, in combination, a machine frame including guide rail means extending in upward direction; a tub supported on said guide rail means movable from a lower rest position to an upper discharge position; a shaft turnably mounted in said tub and having opposite ends extending respectively beyond opposite sides of said tub; mixing means in said tub mounted on said shaft means for rotation therewith; a single drive shaft turnably mounted on said frame means; a pair of pulleys respectively fixedly mounted on said opposite ends of said shaft means for rotation therewith; a pair of ropes respectively wound in several turns about said pulleys; and a pair of composite drums fixedly mounted on said drive shaft for rotation therewith and having each two drum portions, at least one of said drum portions of each composite drum being constructed as a two-step drum portion, each of said ropes having a pair of free ends respectively fastened to said two drum portions of said pair of composite drums, the end portions of said ropes being wound on said two drum portions in opposite directions and the diameters of said two-step drum portion being dimensioned to the diameter of the other drum portion in each composite drum so that during turning of said drive shaft in one direction each rope first unwinds from one drum portion of each composite drum at least to the same extent as it is wound on the other drum portion so that said shaft means are rotated without moving said tub between said positions thereof while during further rotation of said drive shaft in said one direction each rope is wound to a greater extent on said other drum portion than it is unwound from said one drum portion so as to move said tub between said positions thereof while simultaneously turning said shaft means.

2. A concrete mixing and lifting apparatus as set forth in claim 1 in which the diameters of said pulleys are considerably greater than the maximum diameters of said composite drums.

3. A concrete mixing and lifting apparatus as set forth in claim 1, wherein said pair of pulleys on the shaft of the mixing device are provided each with a rope-guiding device in the form of a cylindrical casing around said pulley, entrance and exit openings in said casing for said rope, a helical rope-guiding groove formed on the inner wall of said casing, guide rollers provided in said casing and arranged in contact with the plain circumference of said pulley, and a guide arm with a rope-guiding loop secured to said casing in the zone of one of said openings.

4. A concrete mixing and lifting apparatus as set forth in claim 1, wherein said pair of pulleys on said shaft 9 means of the mixing device are provided with tapered lateral rope-guiding flanges, the annular groove formed by these flanges having a width equal a multiple of the thickness of said ropes.

5. A concrete mixing and lifting apparatus as set forth in claim 1 wherein each of said pulleys of said shaft means is formed with a continuous helical rope guiding groove, and including a rope guiding device in form of a cylindrical casing around each pulley, each of said casings being formed with an entrance and an exit opening for the rope cooperating with the respective pulley, a plurality of guide pins projecting from the inner surface of each casing into engagement with said guide grooves, and a guide arm projecting from each casing in the region of one of said openings and having a rope guiding loop secured to the free end thereof.

6. A concrete mixing and lifting apparatus as set forth in claim 1 and including an additional composite drum having two drum portions at least one of which being constructed as a two-step drum portion, said additional composite drum being fixedly mounted on said drive shaft and forming part of a rope and tackle control device.

7. A concrete mixing and lifting apparatus as set forth in claim 6, wherein said rope and tackle control device comprises a rope to be uncoiled from one drum step of said additional composite drum and to be wound up on another drum step, a loose pulley carried by said rope, a link member carried by said loose pulley, and a rope guided over suitably arranged guide pulleys and connected with said link member and with a fixed point of said tub for controlling the position of said tub and the operation of the mixing means therein.

8. A concrete mixing and lifting apparatus comprising, in combination, a machine frame including guide rail means extending in upward direction; a tub supported on said guide rail means movable from a lower rest position to an upper discharge position; a shaft turnably mounted in said tub and having opposite ends extending respectively beyond opposite sides of said tub; mixing means in said tub mounted on said shaft means for rotation therewith; a single drive shaft turnably mounted on said frame means; a pair of pulleys respectively fixedly mounted on said opposite ends of said shaft means for rotation therewith; a pair of ropes respectively wound in several turns about said pulleys; and a pair of composite drums fixedly mounted on said drive shaft for rotation therewith and having each two drum portions, one of said drum portions of each composite drum being a cylindrical drum portion and the other of said drum portions having a first cylindrical step of a diameter larger than the diameter of said one drum portion, a second cylindrical step of a diameter substantially equal to that of said one drum portion, and a conical transition portion between said first and second cylindrical steps, each of said ropes having a pair of free ends respectively fastened to said two drum portions of said pair of composite drums, the end portions of said ropes being wound on said two drum portions in opposite directions so that during turning of said drive shaft in one direction each rope first unwinds from said cylindrical portion of said one drum portion to the same extent as it is wound on said second cylindrical step of said other drum portion so that said shaft means are rotated without moving said tub between said positions thereof while during further rotation of said drive shaft in said one direction each rope is wound first on said conical transition portion and then on said first cylindrical step so that each rope is wound to a greater extent on said other drum portion than it is unwound from said one drum portion so as to move said tub between said positions thereof while simultaneously turning said shaft and whereby said tub is gradually accelerated at the start of its movement.

9. A concrete mixing and lifting apparatus as set forth in claim 8, wherein one of the free ends of each of said ropes is fastened on said one cylindrical drum portion and 10 the other free end on second drum step of said two-step drum portion of the respective composite rope drum.

10. A concrete mixing and lifting apparatus as set forth in claim 8 in which said transition portion and at least said second cylindrical step of said other drum portion are provided with a continuous helical rope guiding groove.

11. A concrete mixing and lifting apparatus comprising, in combination, a machine frame including guide rail means extending in upward direction; a tub supported on said guide rail means movable from a lower rest position to an upper discharge position; a shaft turnably mounted in said tub and having opposite ends extending respective ly beyond opposite sides of said tub; mixing means in said tub mounted on said shaft means for rotation therewith; a single drive shaft turnably mounted on said frame means; a pair of pulleys respectively fixedly mounted on said opposite ends of said shaft means for rotation therewith; a pair of ropes respectively wound in several turns about said pulleys; and a pair of composite drums fixedly mounted on said drive shaft for rotation therewith and having each two drum portions, one of said drum portions of each composite drum being a conical drum portion provided with a continuous helical rope guiding groove and the other of said drum portions being a two-step drum portion having a first drum step formed by a cylindrical body and a second drum step formed by a deep annular groove at one end of said cylindrical body, the width of said groove being equal to the thickness of said ropes and the diameter of said groove at its bottom being substantially smaller than that of the smaller end of said conical drum portion, each of said ropes having a pair of free ends respectively fastened to said two drum portions of said pair of composite drums, the end portions of said ropes being wound on said two drum portions in opposite directions.

12. A concrete mixing and lifting apparatus as set forth in claim 11, wherein one of the free ends of each of said ropes is fastened on said conical drum portion and the other free end on the groove bottom of said two-step drum portion of the respective composite rope drum.

13. A concrete mixing and lifting apparatus comprising, in combination, a machine frame including guide rail means extending in upward direction; a tub supported on said guide rail means movable from a lower rest position to an upper discharge position; a shaft turnably mounted in said tub and having opposite ends extending respectively beyond opposite sides of said tub; mixing means in said tub mounted on said shaft means for rotation therewith; a single drive shaft turnably mounted on said frame means; a pair of pulleys respectively fixedly mounted on said opposite ends of said shaft means for rotation therewith; a pair of ropes respectively wound in several turns about said pulleys; and a pair of composite drums fixedly mounted on said drive shaft for rotation therewith and having each two drum portions, one of said drum portions being constituted by a circumferentially grooved rope pulley, the groove of which has a substantial depth and a width equal to the thickness of said ropes, and the second drum portion being a two-step drum portion having a first drum step formed by a cylindrical body and a second drum step formed by a deep annular groove at one end of said cylindrical body, the width of said annular groove being equal to the thickness of said ropes and the diameter of said groove on its bottom being substantially smaller than that of said grooved pulley on its grooved bottom, each of said ropes having a pair of free ends respectively fastened to said two drum portions of said pair of composite drums, the end portions of said ropes being wound on said two drum portions in opposite directions.

14. A concrete mixing and lifting apparatus as set forth in claim 13, wherein one of the free ends of each of said ropes is fastened on the groove bottom of said rope pulley of the respective composite rope drum and the other free 1 1 end is fastened on the groove bottom of the two-step drum 1,861,416 portion of the respective composite drum. 2,855,162 References Cited in the file of this patent 2923491 UNITED STATES PATENTS 5 1,533,950 Schlich Apr. 14, 1925 1 1,812,823 Eggert June 30, 1931 1,092,437

Jaeger May 31, 1932 Schacht Oct. 7, 1958 Fischer Feb. 2, 1960 FOREIGN PATENTS France Oct. 23, 1953 

1. A CONCRETE MIXING AND LIFTING APPARATUS COMPRISING, IN COMBINATION, A MACHINE FRAME INCLUDING GUIDE RAIL MEANS EXTENDING IN UPWARD DIRECTION; A TUB SUPPORTED ON SAID GUIDE RAIL MEANS MOVABLE FROM A LOWER REST POSITION TO AN UPPER DISCHARGE POSITION; A SHAFT TURNABLY MOUNTED IN SAID TUB AND HAVING OPPOSITE ENDS EXTENDING RESPECTIVELY BEYOND OPPOSITE SIDES OF SAID TUB; MIXING MEANS IN SAID TUB MOUNTED ON SAID SHAFT MEANS FOR ROTATION THEREWITH; A SINGLE DRIVE SHAFT TURNABLY MOUNTED ON SAID FRAME MEANS; A PAIR OF PULLEYS RESPECTIVELY FIXEDLY MOUNTED ON SAID OPPOSITE ENDS OF SAID SHAFT MEANS FOR ROTATION THEREWITH; A PAIR OF ROPES RESPECTIVELY WOUND IN SEVERAL TURNS ABOUT SAID PULLEYS; AND A PAIR OF COMPOSITE DRUMS FIXEDLY MOUNTED ON SAID DRIVE SHAFT FOR ROTATION THEREWITH AND HAVING EACH TWO DRUM PORTIONS, AT LEAST ONE OF SAID DRUM PORTIONS OF EACH COMPOSITE DRUM BEING CONSTRUCTED AS A TWO-STEP DRUM PORTION, EACH OF SAID ROPES HAVING A PAIR OF FREE ENDS RESPECTIVELY FASTENED TO SAID TWO DRUM PORTIONS OF SAID PAIR OF COMPOSITE DRUMS, THE END PORTIONS OF SAID ROPES BEING WOUND ON SAID TWO DRUM PORTIONS IN OPPOSITE DIRECTIONS AND THE DIAMETERS OF SAID TWO-STEP DRUM POR- 